Tungsten addition agent



United States Patent 3,372,021 TUNGSTEN ADDITION AGENT Edward C. Forbes, deceased, late of Lewiston, N.Y., by Marjorie I. Forbes, executrix, Lewiston, Daniel H. Barbour, Niagara Falls, and Charles M. Brown, Lewiston, N.Y., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Filed June 19, 1964, Ser. No. 376,550 5 Claims. (Cl. 75-.5)

The present invention relates to addition agents for use in the manufacture of steel. More particularly, the present invention relates to a tungsten-containing addition agent which is rapidly dissolved in molten steel and which provides high recoveries of tungsten.

Up to the present, tungsten addition agents have been made mostly as ferrotungsten alloy containing from 78- 82% tungsten and such material has been generally added to steel baths in the form of particles sized on the order of inch. While ferrotungsten alloy used in this manner provides certain advantages, the solution times required and concurrent decrease in the bath temperature are drawbacks which limit the effectiveness of this material.

'It is therefore an object of the present invention to provide a tungsten addition agent which is rapidly soluble in molten steel.

It is another object of the present invention to provide a tungsten addition agent which does not cause an excessive decrease in the temperature of the steel bath in which it is used.

It is a further object of the present invention to provide a tungsten addition agent for use in the manufacture of steel which provides high tungsten recoveries.

Other objects will be apparent from the following description and claims.

An addition agent in accordance with the present invention is a pressed mixture of tungsten powder and iron powder containing at least about 15% iron by weight and at least about 50% tungsten by weight.

In the preparation of the addition agent of the present invention iron powder, the predominant proportion being sized from 48 to 200 mesh, is blended with tungsten powder of which the predominant proportion is sized 100 to microns.

The indicated sizing of the iron and tungsten powder is important in order to provide a product having the desired structure hereinafter described.

The proportions of iron and tungsten in the mixture are also important for the purpose of providing suitable handling strength and density. The preferred ranges for iron and tungsten are -35% and 65-85%, respectively.

When a suitable blended mixture of iron and tungsten powder is provided in accordance with the present invention, the mixture is pressed by powder metallurgical techniques into convenient forms having a density of between 50 and 75% of the maximum theoretical density of the mixture. For example the mixture can be pressed into pellets using conventional steel dies. With a mixture containing iron (sized mostly 48 mesh with some finer particles) and 80% W (sized 10-50 microns), a pressure of 4000 p.s.i. can be used to form /8" diameter pellets which are sponge-like in structure and have a suitable density.

The article formed in the foregoing manner is characterized by a structure and density and strength characteristics which substantially improve its effectiveness as an addition agent.

For example, the structure of the compressed irontungsten mixture is porous and comprises a matrix of iron in which the tungsten particles, in substantially their original size and shape, are embedded. That is to say, the tungsten powder is effectively densified without significantly affecting the sizing of the powder. Consequently, upon addition to molten steel, the fine tungsten particles are released and dissolve rapidly while the losses ordinarily encountered with tungsten powder additions are avoided. Also, the density of the compressed irontungsten mixture of this invention is such that it does not sink rapidly but descends through a molten steel bath at a convenient and effective rate.

In a further embodiment of the present invention, the pressed articles formed in the foregoing manner are sintered during or after pressing so as to provide increased handling strength.

The sintering temperature and time used is such that the density of the pressed article is not increased outside of the aforementioned range.

By way of example, with a pellet (20% Fe, W) pressed from a mixture (Fe sized 48-200 mesh; W sized 10-50 microns) at a pressure of 4000 p.s.i., sintering at a temperature of 1400 C. for 15 minutes provides an addition agent having the desired structure, excellent handling strength and satisfactory density.

The following examples will further illustrate the present invention.

Example I A 50 gram blended mixture of tungsten powder and iron powder was prepared. The tungsten, 80% of the mixture, was sized 10-50 microns and the iron, 20% of the mixture, was sized 48-200 mesh.

Pellets (0.253 in. x 0.387 in. diameter) were produced by pressing in dies at 4000 p.s.i. After pressing the pellets were sintered in a tungsten boat at 1400" C. for 15 minutes. The resulting articles had a density of 8.63 g./cc.

Example II The same procedure was used as in Example I except that the mixture was 50% W, 50% Fe. The articles obtained had a density of 6.9 g./cc.

Example III A 250 lb. blended mixture of tungsten powder and iron powder was prepared. The tungsten, 80% of the mixture, was sized 10-50 microns and the iron, 20% of the mixture, was sized 48-200 mesh.

The mixture was passed through 16 inch diameter rolls three times at a roll pressure of 19,000-26,000 lbs. per inch of roll face to provide a sheet product about 4; inch thick having a density of 10 g./ cc. The sheet product was then sintered at 1350 C. for about 4 hours in a Globar furnace. The density of the sintered material was about 10 g./cc.

Example lV Example V The same procedure as in Example III was followed with a 50% W, 50% Fe mixture except that 4 roll passes were made.

The density of the sheet material was 8.2 g./oc. and the density of the sintered material was about 8.3 g./cc.

manner to provide a comparison. The results are shown in Table I.

TABLE I Solution Temp. Percent Addition Agent Time, Drop, Re-

seconds C. covery Standard (79.18% W) ferrotungsten- 38 14 94 30% ferrotnngsten. 60 29 93 80% W, 20% Fe (Example III) 21 I 7 87 50% w, 50% Fe (Example 1v 30 14 edmixture with iron and at least the stoichiometric amount of carbon for forming CO, the solution time is significantly decreased and tungsten recoveries are im* proved. This occurs due to the formation and evolution of carbon monoxide gas, upon reaction of the contained oxygen and-carbon.

.Although the foregoing description has referred specifically to the use of iron powder, nickel powder can be substituted for all or part of the iron.

The mesh sizes referred to herein are Tyler Standard Series.

What is claimed is: v

1. As an alloy addition agent, a pressed mixture of elemental tungsten powder and elemental iron powder consisting essentially of about 50 to 80% tungsten and about 20 to iron having a density between 50 and of the theoretical density of the mixture and char acterized by having an iron matrix in which the tungsten powder particles, in substantially their original size and shape, are embedded, the original particle sizing of the iron powder being substantially from about 48 to 200 mesh and the original sizing of the tungsten powder being substantially 10 to 50 microns. v

2. An addition agent in accordance with claim 1 consisting essentially of about tungsten and about 20% iron.

3. An addition agent in accordance with claim 1 consisting essentially of about 50% tungsten and about 50% iron.

4. An addition agent in accordance with claim 1 in which the tungsten powder has an oxygen content of from about 0.10 to 0.25% and in which carbon is included in at least the stoichiometric amount to combine with said oxygen to form carbon monoxide. f

5. An addition agent in accordance with claim 1 Wherein the original particle sizing of the iron powder is substantially all in the range of 48 to 200 mesh and the original sizing of the tungsten powder is substantially all in the range of 10 to 50 microns.

References Cited UNITED STATES PATENTS 1,775,358 9/1930 Smith. 2,302,616 11/1942 Linz 75--l22 2,763,918 9/1956 Megill 75176 DAVID L. RECK, Primary Examiner.

HYLAND BIZOT, Examiner.

35 W. STALLARD, Assistant Examiner. 

1. AS AN ALLOY ADDITION AGENT, A PRESSED MIXTURE OF ELEMENTAL TUNGSTEN POWDER AND ELEMTA IRON POWDER CONSISTING ESSENTIALLY OF ABOUT 50 TO 80% TUNGSTEN AND ABOUT 20 TO 50% IRON HAVING A DENSITY BETWEEN 50 AND 75% OF THE THEORETICAL DENSITY OF THE MIXUTRE AND CHARACTERIZED BY HAVING AN IRON MATRIX IN WHICH THE TUNGSTEN POWDER PARTICLES, IN SUBSTANTIALLY THEIR ORIGINAL SIZE AND SHAPE, ARE EMBEDDED, THE ORIGINAL PARTICLE SIZING OF THE IRON POWDER BEING SUBSTANTIALLY FROM ABOUT 48 TO 200 MESH AND THE ORGINAL SIZING OF THE TUNGSTEN POWDER BEING SUBSTANTIALLY 10 TO 50 MICRONS. 